1. Field of the Invention
The present invention relates to a screw compressor having a slide valve for adjusting a volume of discharged gas.
2. Description of the Related Art
A screw compressor having a slide valve to adjust the volume of discharged gas has heretofore been known publicly.
It is preferable for the slide valve to be superior in its operation responsivity so that the screw compressor can discharge compressed gas without excess or deficiency in the amount of the gas required in accordance with a change in the amount of consumption of the compressed gas discharged. However, in case of the slide valve being actuated by an ordinary type of a hydraulic cylinder and in case of the hydraulic cylinder being a single hydraulic cylinder, the operation of the slide valve becomes slow and the responsivity in operation, i.e., the responsivity in volume control, of the slide valve is poor.
For improving the responsivity it is necessary to increase the power for actuating the slide valve. The power may be increased by enlarging the diameter of a piston in the hydraulic cylinder or by using pressurizing means for increasing the oil pressure. However, in view of the structure of the screw compressor, a limit is in many cases encountered in increasing the diameter of the piston. Further, the addition of pressurizing means for increasing the oil pressure leads to a more complicated configuration of equipment concerned.